The decline in the number of children nationally being vaccinated against pertussis has caused anxiety and concern, both for parents and for professional workers. Publicity by the media and professional press has added to the confusion, and has been largely held responsible for the present situation. A survey was undertaken to analyse the factors which may have been responsible for the reduction in the number of children coming forward for pertussis vaccination in Leicestershire. These factors included social class, the position of the child within the family, and the reasons given by families for omission of the vaccine. Observations on the computerized record of immunization and vaccination, and the family's own record of the dates of immunization were made. The results of the survey present a more complicated picture than expected, with the consequence that solutions are difficult to find.